CMP device and production method for semiconductor device

ABSTRACT

A triangular pad of the type shown in FIG.  5  ( a ) which has circular tip ends is used as the polishing pad. This shape corresponds to the concept of partially cutting the outer edge of the polishing pad in order to shorten the contact time of the polishing pad and wafer at the outer circumference of the wafer regardless of the swing speed. As shown in the figure, a circular bored part with a diameter of 50 mm is provided in the center of such a polishing pad. By using this polishing pad and dividing the swing width into ten, it is possible to keep the product of the integrated value of the relative linear velocity, the integrated value of the pressure, and the integrated value of the contact time at various points within the wafer surface within ±30% of the mean value in each swing width under feasible swing conditions. Thus, the use of such a polishing pad makes it possible to perform uniform polishing.

TECHNICAL FIELD

[0001] The present invention relates to a CMP apparatus (chemicalmechanical polishing apparatus) in which both chemical polishing andmechanical polishing are performed by causing relative movement of apolishing pad and an object of polishing while supplying a polishingagent (slurry) between the polishing pad and the object of polishing.

BACKGROUND ART

[0002] In universally known CMP apparatuses (Japanese Patent ApplicationKokai No. H6-21028, Japanese Patent Application Kokai No. H7-266219,Japanese Patent Application Kokai No. H8-192353, Japanese PatentApplication Kokai No. H8-293477, Japanese Patent Application Kokai No.H10-173715, Japanese Patent Application Kokai No. H11-156711 and BritishLaid-Open Patent No. 2331948, etc.), an object of polishing is polishedby supporting a surface plate on which a polishing pad is pasted on aspindle shaft, causing this surface plate to rotate, rotating the objectof polishing that is held on a chuck that faces this, pressing theobject of polishing that is held on a chuck against the surface of thepolishing pad while supplying a polishing agent (slurry) to thissurface, causing the pad and object of polishing to rotate in the samedirection or in opposite directions in relative terms, and swinging thepolishing pad.

[0003] Polishing pad materials that are used include hard foam urethanesheets, polyester fiber nonwoven fabrics, felt, polyvinyl alcohol fibernonwoven fabrics, nylon fiber nonwoven fabrics, and materials in which afoaming urethane resin solution is flow-spread on such nonwoven fabrics,and is then foamed and hardened, etc.

[0004] Conventionally, the polishing pad shape has been circular, likethe shape of the substrate that is being polished, and pads with athickness of 3 to 7 mm have been used in a configuration in which thesepads are pasted to a surface plate such as an aluminum plate orstainless steel plate.

[0005] Furthermore, pads that are larger than the object of polishinghave been used as polishing pads in the past; however, for reasons suchas the difficulty in uniform polishing caused by the increaseddifference between the peripheral speed in the outer portion and theperipheral speed in the central portion, and the difficulty inhigh-speed rotation of a surface plate that has large dimensions,so-called small-diameter pads, which have a smaller size than that of anobject of polishing, have come to be used recently.

[0006] Generally, a Preston's equation such as the one shown below isused as an equation for determining the amount of polishing:

V=n·P·v·t

[0007] Here, V is the polishing speed, n is a constant, P is the contactpressure of the polishing pad and object of polishing, v is the relativelinear velocity of the polishing pad and object of polishing, and t isthe contact time of the polishing pad and object of polishing. In orderto perform uniform polishing, the polishing speed determined by V mustbe more or less the same at each point of the object of polishing.

[0008] In the case of a polishing system using a small-diameter pad, aportion of the object of polishing is polished at any given moment, sothat a polishing method is used under swing conditions in which thepolishing pad overhangs from the object of polishing in order to ensurehigh-speed polishing and polishing uniformity.

[0009] However, when the polishing pad overhangs from the object ofpolishing, the contact area between the polishing pad and object ofpolishing fluctuates due to swinging, so that the load per unit areafluctuates. Furthermore, in cases where the diaphragm system of apressure mechanism is used, inclination of the polishing pad andfluctuation of the load occur due to the overhang from the object ofpolishing. As a result, the product of the integrated value of the loadand the integrated value of the relative linear velocity during thepolishing time does not show the same value at various points within thesurface of the object of polishing. In other words, polishing isperformed unevenly.

[0010] Therefore, to keep this value the same, a method is employed inwhich the swing speed is varied according to the swing position(adjustment is made according to the contact time between the object ofpolishing and polishing pad), or the load is controlled so as to beconstant.

[0011] [Problems to be Solved by the Invention]

[0012] However, in cases where the swing speed is varied according tothe swing position, the following problems are encountered:specifically, the conditions of varying the speed to achieve the uniformpolishing become complex, and the machinery cannot catch up with thecommand speed determined. Furthermore, in cases where the pressure iscontrolled according to the swing position so that the load per unitarea is constant, the problem is that there may be delay in control dueto the compression of the fluid, etc., used for pressurization. Becauseof these problems, it is difficult to uniformly polish objects ofpolishing in a polishing apparatus using a small-diameter pad.

DISCLOSURE OF THE INVENTION

[0013] The present invention was devised in light of such facts, and theobject of the present invention is to provide a CMP apparatus capable ofuniformly polishing an object of polishing even in cases where asmall-diameter pad is used, and a semiconductor device manufacturingmethod utilizing this CMP apparatus.

[0014] The first invention that is used to achieve the above-mentionedobject is a CMP apparatus (chemical mechanical polishing apparatus)which performs polishing by pressing a polishing pad that is smallerthan the object of polishing against the object of polishing in relativeterms and by swinging the polishing pad while rotating both the objectof polishing and the polishing pad so that relative movement occursbetween these two parts, wherein this CMP apparatus comprises apolishing pad whose shape is such that in all points on the surface ofthe object of polishing, the product of three values—i.e., theintegrated value of the relative linear velocity, the integrated valueof the pressure, and the integrated value of the contact time—of thepolishing pad and object of polishing during the polishing time iswithin ±30% of the mean value of the product of these three integratedvalues at all points on the surface of the object of polishing.

[0015] In the present invention, as a result of the design of thepolishing pad shape, the product of the three elements in theabove-mentioned Preston's equation is maintained within a specifiedrange over the entire surface of the object of polishing. Specifically,a polishing pad is used which has a shape such that in all points on thesurface of the object of polishing, the product of three values—i.e.,the integrated value of the relative linear velocity, the integratedvalue of the pressure, and the integrated value of the contact time—ofthe polishing pad and object of polishing during the polishing time iswithin ±30% of the mean value of the product of these three integratedvalues at all points on the surface of the object of polishing.

[0016] The shape of such a polishing pad changes according to the ratioof the polishing pad to the object of polishing and the swing range ofthe polishing pad, etc., and the present invention is realized generallyby making this shape so that the contact time of the object of polishingand polishing pad is shortened toward the outer circumferential portionof the polishing pad by cutting the outer circumferential portion of thepolishing pad, where the peripheral speed is faster. The reason that therange of dispersion of the above-mentioned product of the threeintegrated values is kept within ±30% of the mean value is that it hasbeen found as a result of experiments by the inventors that if thisdispersion is kept within this range, the uniform polishing of a siliconwafer is possible in a range that does not cause practical problems in aCMP apparatus.

[0017] In the present invention, since the shape of the polishing pad issuch that the above-mentioned conditions are satisfied, there is no needto perform complicated swinging, and swinging in a range that allows themachinery to catch up is sufficient; accordingly, it is possible toperform uniform polishing over the entire surface of the object ofpolishing. The symmetry of the external shape of the polishing pad isnot absolutely necessary.

[0018] The second invention that is used to achieve the above-mentionedobject is the above-mentioned first invention, wherein at least onebored part is provided in the polishing pad.

[0019] It is preferable that the bored part be provided in the centralportion, where the peripheral speed of rotation is slow. By doing so,polishing is not performed in the area where the peripheral speed ofrotation is slow, which reduces the distribution of the relative speedof the polishing pad and the member to be polished in various parts thatcontact the polishing pad, which in turn makes it easier to satisfy theconditions in the above-mentioned first invention. The symmetry of thebored shape is not absolutely necessary. Furthermore, the position ofthe bored part does not have to be symmetrical to the center of theexternal shape of the polishing pad or the center of rotation of therotating surface plate to which the polishing pad is fixed.

[0020] The third invention that is used to achieve the above-mentionedobject is the above-mentioned second invention, wherein the area of thebored part is 80% or less of the total area of the pad.

[0021] In the second invention, if the area of the bored part isexcessively large, not only can the uniformity of polishing notmaintained even more, but also the polishing efficiency deteriorates.According to the experiments by the inventors, if this area exceeds 80%,these characteristics rapidly deteriorate, so that the area is limitedto 80% or less.

[0022] The fourth invention that is used to achieve the above-mentionedobject is the above-mentioned second invention or third invention,wherein a mechanism for supplying a slurry from the bored part isprovided.

[0023] A slurry that constitutes the polishing agent is supplied betweenthe polishing pad and object of polishing in a CMP apparatus; however,if the slurry is supplied from the outside of the polishing pad, theslurry is scattered due to the centrifugal force accompanied by therotation of the object of polishing, so that there are cases in whichthe slurry does not enter between the polishing pad and object ofpolishing very well. In the present invention, since the slurry issupplied from the bored part in the polishing pad, this polishing agentis supplied between the polishing pad and the object of polishingwithout scattering.

[0024] The fifth invention that is used to achieve the above-mentionedobject is any of the above-mentioned second invention through fourthinvention, wherein the shape of the above-mentioned bored part is ashape other than a circle.

[0025] In the present invention, the location of the boundary betweenthe bored part and the remaining parts changes with the rotation of thepolishing pad even in cases where the center of rotation of thepolishing pad coincides with the bored part; accordingly, it is possibleto prevent polishing at the boundary portion from becoming non-uniform.

[0026] The sixth invention that is used to achieve the above-mentionedobject is the above-mentioned first invention, wherein a circular boredpart is provided in the center of the polishing pad, and when the radiusof this bored part is r, the length of the effective part of thepolishing pad on the circumference in the specified distance from thecenter of the above-mentioned polishing pad is in the range of 0.5 πr to4 πr, excluding the end parts of the above-mentioned polishing pad.

[0027] Here, the “end parts” refer to the areas that are located withina distance of 5 mm from the corner parts of the member forming thepolishing pad, or the areas that are located within a distance of 5 mmfrom the vertices of a polygonal shape that is formed by extending thelines forming the edge parts of the polishing pad.

[0028] In the present invention, since the shape of the polishing padsatisfies such a condition, there is no need to perform complicatedswinging, and swinging within a range that allows the machinery to catchup is sufficient. Accordingly, it is possible to perform uniformpolishing over the entire surface of the object of polishing. Thesymmetry of the external shape of the polishing pad is not absolutelynecessary.

[0029] In contrast, when the length of the effective part of thepolishing pad in the specified distance from the center of theabove-mentioned polishing pad is not in the range of 0.5 πr to 4 πr,complex swinging must be performed, so that the machinery cannot catchup. Furthermore, the reason that this condition is excluded in theabove-mentioned end parts is that the ratio of the end partscontributing to polishing is small, so that these parts can be ignored.

[0030] The seventh invention that is used to achieve the above-mentionedobject is any of the above-mentioned first invention through sixthinvention, wherein the center of the external shape of the polishing padand the center of rotation of the surface plate to which the polishingpad is pasted are shifted.

[0031] If the center of the external shape of the polishing pad and thecenter of rotation of the surface plate to which the polishing pad ispasted coincide with each other, the outer circumferential portion ofthe polishing pad always rotates in a state in which the linear velocityis fast, while the central portion always rotates in a state in whichthe linear velocity is slow. Accordingly, the difference in linearvelocity is increased, which is undesirable. Furthermore, in cases wherethe bored part is provided in the central portion of the pad in theabove-mentioned second invention, a discontinuous part emerges betweenthe bored part and non-bored part at the end parts of swinging; as aresult, polishing may become non-uniform.

[0032] In the present invention, since the center of the external shapeof the polishing pad and the center of rotation of the surface plate towhich the polishing pad is pasted are shifted, the difference in linearvelocity within the polishing pad is reduced, so that the amount ofpolishing of the object of polishing can be made even more uniform.Moreover, since complex swinging is practically applied, it is possibleto prevent the occurrence of the discontinuous part between the boredpart and non-bored part in the end parts of swinging even in cases wherethe central part of the polishing pad is bored through.

[0033] The eighth invention that is used to achieve the above-mentionedobject is a semiconductor device manufacturing method comprising aprocess in which a wafer is polished using the CMP apparatus of any ofthe above-mentioned first invention through seventh invention.

[0034] In the present invention, polishing of a wafer can be performedwith a high degree of uniformity, so that semiconductor devices thathave a fine line width can be manufactured with a good yield.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035]FIG. 1 is a perspective view showing one example of the CMPapparatus that constitutes an embodiment of the present invention.

[0036]FIG. 2 is a perspective view showing a feeding mechanism of thepolishing pad.

[0037]FIG. 3 is a partial sectional view of the polishing pad andconditioning device.

[0038]FIG. 4 is a sectional view of the polishing head.

[0039]FIG. 5 are diagrams showing examples of the polishing pad in anembodiment and a comparative example.

[0040]FIG. 6 is a graph showing the swing speed in an embodiment of thepresent invention.

[0041]FIG. 7 is a graph showing the result of polishing a wafer in thefirst embodiment of the present invention.

[0042]FIG. 8 is a graph showing the swing speed in a comparativeexample.

[0043]FIG. 9 is a graph showing the result of polishing a wafer in acomparative example.

[0044]FIG. 10 is a diagram illustrating the polishing pad in the secondembodiment of the present invention.

[0045]FIG. 11 is a graph showing the result of polishing a wafer in thesecond embodiment of the present invention.

[0046]FIG. 12 is a diagram illustrating the polishing pad in the thirdembodiment of the present invention.

[0047]FIG. 13 is a flow chart illustrating the semiconductor devicemanufacturing process.

BEST MODE FOR CARRYING OUT THE INVENTION

[0048] Preferred embodiments of the present invention will be describedbelow using the figures. However, the scope of the present invention isnot limited by the embodiments described.

[0049]FIG. 1 is a perspective view showing one example of the CMPapparatus constituting an embodiment of the present invention. FIG. 2 isa perspective view showing a feeding mechanism of the polishing pad.FIG. 3 is a partial sectional view of the polishing pad and theconditioning device. FIG. 4 is a sectional view of the polishing head.

[0050] In the indexing-type CMP apparatus 1 shown in FIGS. 1, 2 and 3, 2indicates a polishing head, 2 a indicates a polishing head used forrough polishing, 2 b indicates a polishing head used for finishingpolishing, 3 indicates a rotating shaft, 3 a indicates a motor, 3 bindicates a gear, 3 c indicates a pulley, 3 d indicates a gear, 4indicates polishing pads, 5 indicates pad conditioning mechanisms, 5 aindicates a dressing disk, 5 b indicates a spray nozzle, 5 c indicates aprotective cover, 6 indicates rotatable cleaning brushes, 7 indicates afeeding mechanism for the polishing head, 7 a indicates a rail, 7 bindicates a feed screw, and 7 c indicates a moving body which isscrew-mounted on the feed screw, with the polishing head being held onthis moving body.

[0051]7 d and 7 e indicate gears, 7 f indicates a motor, 8 indicates anair cylinder constituting a head raising-and-lowering mechanism, 9indicates a cassette that accommodates wafers W, 10 indicates aloading-conveying robot, and 11 indicates a wafer temporary placementstand. 12 indicates an indexing table which has four rotatable waferchucking mechanisms 12 a, 12 b, 12 c and 12 d installed at equalintervals on the same circle centered on a shaft 12 e; this indexingtable 12 is divided into a wafer loading zone s1, a rough polishing zones2, a wafer finishing polishing zone s3, and a wafer unloading zone s4.

[0052]13 indicates an unloading-conveying robot, 14 a indicates a chuckdresser, 14 b indicates a chuck cleaning mechanism, 15 indicates a wafertemporary placement stand, 16 indicates a belt conveyor, and 17indicates a wafer cleaning mechanism.

[0053] In the polishing head 2 shown in FIG. 4, the polishing head 2 isdevised so that the protruding edge 21 a of the substrate 21 issupported on the flange part 20 a of a pressurizing cylinder 20, and thepolishing pad (annular polishing cloth) 4 is held on the substrate 21via a polishing cloth attachment plate 22. A diaphragm 23 is installedinside the pressurizing chamber 20 b of the pressurizing cylinder 20,and compressed air is pressure-fed into the interior of the pressurizingchamber 20 b via the interior of the spindle shaft 3. The substrate 21is supported by this pressure so that the substrate 21 is free to swingin three dimensions (X, Y and Z), and the polishing pad 4 is heldparallel to the surface of the wafer.

[0054] A supply pipe 24 for the polishing liquid or cleaning liquid isinstalled in the center of the head 2, and the tip end of this pipe 24faces the back surface of the annular body of the polishing pad (whileavoiding the central bored part 4 a of the polishing pad 4), so that thepolishing liquid is supplied to the surface of the substrate via theannular body. Furthermore, instead of using this configuration, the pipemay be configured so that the polishing liquid is supplied to theinterior of the central bored part 4 a of the polishing pad 4.

[0055] A hard foam urethane sheet, polyester fiber nonwoven fabric,felt, polyvinyl alcohol fiber nonwoven fabric, nylon fiber nonwovenfabric, or a material in which a urethane resin solution is flow-spreadon such a nonwoven fabric and is then foamed and hardened, etc., is usedas the polishing pad material. The thickness of the pad is 1 to 7 mm.Furthermore, laminates of the above-mentioned materials may also beutilized.

[0056] A slurry which contains the following materials is used as thepolishing agent liquid: (a) solid abrasive grains of colloidal alumina,fumed silica, cerium oxide or titania, etc., at the rate of 0.01 to 20wt %, (b) an oxidizing agent such as copper nitrate, iron citrate,manganese peroxide, ethylenediaminetetraacetic acid, hexacynao-iron,hydrofluoric acid, fluorotitanic acid, dipersulfate, ammonium fluoride,ammonium hydrogen difluoride, ammonium persulfate or hydrogen peroxideat the rate of 1 to 15 wt %, (c) a surfactant at the rate of 0.3 to 3 wt%, (d) a pH adjusting agent, and (e) a preservative, etc. (this isdescribed in Japanese Patent Application Kokai No. H6-313164, JapanesePatent Application Kokai No. H8-197414, Japanese Patent ApplicationTokuhyo No. H8-510437, Japanese Patent Application Kokai No. H10-67986,and Japanese Patent Application Kokai No. H10-226784, etc.).

[0057] Polishing agent slurries that are suitable for the polishing ofmetals such as copper, copper-titanium, copper-tungsten andtitanium-aluminum can be obtained from Fujimi Incorporated, Rodel NittaCompany, Cabot Corporation (U.S.A.) and Rodel, Inc. (U.S.A.).

[0058] The process whereby a wafer that has a metal film on top of aninsulating layer is polished using the above-mentioned CMP apparatus isperformed as follows:

[0059] 1) The wafer w1 (although the wafer is shown as W in the figures,the first wafer is referred to as w1, the second wafer is referred to asw2, and so forth) is removed from the cassette 9 by the arm of theconveying robot 10 and is placed on the temporary placement stand 11with the metal film surface facing upward. Here, the back surface of thewafer is cleaned, and the wafer is then conveyed into the wafer loadingzone s1 of the indexing table 12 by the conveying robot, and issuction-chucked by the chucking mechanism 12 a.

[0060] 2) The indexing table 12 is caused to rotate 90 degrees in theclockwise direction, so that the wafer w1 is conducted into the firstpolishing zone s2. The spindle shaft 3 is lowered so that the polishingpad 4 attached to the head 2 a is pressed against the wafer w1, andchemical mechanical polishing of the wafer is performed by causing thespindle shaft 3 and the shaft of the chucking mechanism to rotate.During this period, a new wafer w2 is placed on the temporary placementstand, and is conveyed into the wafer loading zone s1 andsuction-chucked by the chucking mechanism 12 b.

[0061] During CMP working, the polishing pad is caused to perform areciprocating swinging motion in the left-right direction (the directionof the X axis) by means of a ball screw from the center point of thewafer. The reciprocating swinging motion of the polishing pad is set sothat in a case where the swing speed of the polishing pad when the outercircumference of the polishing pad is positioned between the centerpoint and outer circumference of the wafer is taken as the referencespeed, the swing speed of the polishing pad in the vicinity of thecenter point of the wafer is slowed, and the swing speed in the outercircumferential portion of the wafer is accelerated, so that dishing isevened out.

[0062] When chemical mechanical polishing in the first polishing zone s2has been performed for a desired period of time, the spindle shaft 3 israised and retracted to the right, and is conducted onto a pad cleaningmechanism 5. Here, abrasive grains and metal polishing debris adheringto the pad surface are removed by a rotating brush 6 while ahigh-pressure jet of water is caused to jet from a nozzle 5 b. Then, thepolishing pad is again conveyed to the left, and is caused to wait inthe polishing zone s2.

[0063] 3) The indexing table is caused to rotate 90 degrees in theclockwise direction, so that the polished wafer w1 is conducted into thesecond polishing zone s3. Then, the spindle shaft 3 is lowered so thatthe polishing pad 4 attached to the head 2 b is pressed against theroughly polished wafer w1, and finishing chemical mechanical polishingof the wafer is performed by causing the spindle shaft 3 and the shaftof the chucking mechanism to rotate. After this finishing polishing iscompleted, the spindle shaft 3 is raised and retracted to the right; thepolishing pad attached to the head 2 b is cleaned by the cleaningmechanism 5, and is then again conveyed to the left and caused to waitin the second polishing zone s3.

[0064] During this period, a new wafer w3 is placed on the temporaryplacement stand, conveyed into the wafer loading zone s1, andsuction-chucked by the chucking mechanism 12 c. Furthermore, in thefirst polishing zone s2, rough chemical mechanical polishing of thewafer w2 is performed.

[0065] 4) The indexing table 12 is caused to rotate 90 degrees in theclockwise direction, so that the polished wafer w1 is conducted into theunloading zone s4. Next, the wafer that has been subjected to finishingpolishing is conveyed to the temporary placement stand 15 by theunloading conveying robot 13, and the back surface of this wafer iscleaned. Afterward, this wafer is conducted by the conveying robot 13 toa conveying mechanism that utilizes a belt conveyor, and a cleaningliquid is blown onto the pattern surface of the polished wafer from anozzle 17 so that the pattern surface is cleaned; the wafer is thenconducted to the next process.

[0066] During this period, a new wafer w4 is placed on the temporaryplacement stand; this wafer is conveyed into the wafer loading zone s1,and is suction-chucked by the chucking mechanism 12 b. Furthermore,rough chemical mechanical polishing of the wafer w3 is performed in thefirst polishing zone s2, and finishing chemical mechanical polishing ofthe wafer w2 is performed in the second polishing zone s3.

[0067] 5) The indexing table 12 is caused to rotate 90 degrees in theclockwise direction, after which operations similar to those of theabove-mentioned processes 2) through 4) are repeated, so that chemicalmechanical polishing of the wafers is performed.

[0068] In the above example, the chemical mechanical polishing wasdivided into a first rough polishing process and a second finishingpolishing process in order to shorten the throughput time; however, itwould also be possible to perform CMP working in a single stage, or tofurther shorten the throughput time by dividing the polishing into threestages, i.e., rough polishing, intermediate polishing and finishingpolishing. In cases where a three-stage CMP working process is adopted,s1 is used as a zone for both wafer loading and wafer unloading, s2 isused as a first polishing zone, s3 is used as a second polishing zone,and s4 is used as a third polishing zone.

[0069] Furthermore, in regard to the polishing pad material, thematerials of the first polishing pad and second polishing pad may bevaried.

[0070] Naturally, the CMP apparatus of the present invention may also beused for the removal of the insulating layer film from a substrate inwhich an insulating layer film is formed on top of a metal pattern, orfor the removal of the P-TEOS film layer from an STI.

[0071] (Embodiments)

[0072] Preferred Embodiments of the Present Invention will be DescribedBelow.

[0073] (Embodiment 1)

[0074] Using a CMP apparatus of the type described above, an eight-inchwafer on which a thermal oxidation film had been formed to a thicknessof 1 μm was polished under the following conditions. Polishing wasperformed in two stages in the above-mentioned CMP apparatus; however,since this is an experiment, polishing in the first polishing zone s2was not performed, and polishing only in the second polishing zone s3was performed. The polishing conditions were set as follows:

[0075] Pad rpm: 400 rpm

[0076] Wafer rpm: −200 rpm (rotation in the opposite direction from thepad)

[0077] Load: 200 gf/cm²

[0078] Polishing time: 120 sec

[0079] Slurry: SS25 by Cabot Corporation diluted 2×, 75 ml/min

[0080] Swinging starting position: 25 mm from the center of wafer to thecenter of polishing pad

[0081] Swing width: 40.0 mm from the starting position toward the outercircumference of wafer

[0082] Swing speed: speed variable in ten steps, the width of one of thedivided parts is 4.0 mm

[0083] A triangular pad with the circular tip ends as that shown in FIG.5(a) was used as the polishing pad in this embodiment. (Furthermore, theunits of the dimensions of the polishing pad indicated below are mm.)These circular tip ends correspond to the concept in which portions ofthe outer edge of the polishing pad are cut in order to shorten thecontact time of the polishing pad and wafer in the outer circumferenceof the wafer regardless of the swing speed. As is indicated in thefigure, a circular bored part with a diameter of 50 mm is provided inthe center of such a polishing pad.

[0084] As is shown in FIG. 5(b), a circular polishing pad with adiameter of 150 mm in which a circular bored part with a diameter of 50mm is provided in the center of this polishing pad was used as thepolishing pad for a comparative example.

[0085] Using this polishing pad and dividing the swing width into ten,the respective swing speeds at various swing positions are determined bycalculations so that the product of the integrated value of the relativelinear velocity, the integrated value of the pressure, and theintegrated value of the contact time of the polishing pad and object ofpolishing during the polishing time at various points within the wafersurface in each swing width, is within ±30% of the mean value of theproduct of these three integrated values at all points on the surface ofthe object of polishing. FIG. 6 shows the result in the case of thepolishing pad shown in FIG. 5(a). In FIG. 6, the solid line indicatesthe calculated indicated speed, while circles indicate actually obtainedspeeds. It is seen from this figure that the actually obtained swingspeed follows the command value, and that a desired polishing state isobtained.

[0086]FIG. 7 shows the amount of polishing (in angstroms) obtained inthis polishing. It is apparent from this figure that more or lessconstant amount of polishing is obtained regardless of the measurementpositions. The polishing uniformity (σ) was 12.3%.

[0087]FIG. 8 shows the result, when the polishing pad of the type shownin FIG. 5(b) is used, and the swing width is divided into ten, in whichthe respective swing speeds at various swing positions are determined bycalculations so that the product of the integrated value of the relativelinear velocity, the integrated value of the pressure, and theintegrated value of the contact time of the polishing pad and object ofpolishing during the polishing time at various points within the wafersurface, is within ±30% of the mean value of the product of these threeintegrated values at all points on the surface of the object ofpolishing in each swing width.

[0088] When FIG. 6 and FIG. 8 are compared, it is seen that thefluctuations in the swing speed are increased in the case of FIG. 8.Furthermore, it is also seen that the actually measured values indicatedby the circles do not follow the command values. In other words, in theactual polishing, the following condition is not satisfied; namely, theproduct of the integrated value of the relative linear velocity, theintegrated value of the pressure, and the integrated value of thecontact time of the polishing pad and object of polishing during thepolishing time at various points within the wafer surface, is within±30% of the mean value of the product of these three integrated valuesat all points on the surface of the object of polishing.

[0089] In other words, in the polishing pad having the shape such as theone shown in FIG. 5(b), the condition is not satisfied in which, in allpoints on the surface of the object of polishing, the product of threevalues—i.e., the integrated value of the relative linear velocity, theintegrated value of the pressure, and the integrated value of thecontact time—of the polishing pad and object of polishing during thepolishing time is within ±30% of the mean value of the product of thesethree integrated values at all points on the surface of the object ofpolishing.

[0090]FIG. 9 shows the result in which polishing was performed with theswinging pattern as the one shown in FIG. 8 using the polishing padshown in FIG. 5(b). When the amount of polishing (in angstroms) in FIG.7 and FIG. 9 are compared, it is seen that the fluctuations in thepolishing amount are increased in FIG. 9, which constitutes acomparative example. The reason for this is that the variable speed ofswinging does not effectively act at the outer circumferential part ofthe wafer, so that the polishing speed is high at the periphery of thewafer. The polishing uniformity (σ) was 17.3%.

[0091] (Embodiment 2)

[0092] It is apparent from FIG. 7 that polishing was uneven in the areathat is 50 mm from the center of the wafer. This is the effect of thebored part having a diameter of 50 mm in the pad in FIG. 5(a).Specifically, the edge of the hole is located in the position that is 25mm from the center of the pad, so that a discontinuous part appears inthis area, which affects this creation of uneven parts. In order toavoid this, a polishing pad was created in which the central bored parthas a regular hexagonal shape as shown in FIG. 10, and the remainingshape is the same as the pad shown in FIG. 5(a), and polishing wasperformed under the same swing conditions as those shown in FIG. 6. Thepolishing conditions were the same as in Embodiment 1.

[0093] The result is shown in FIG. 11. According to FIG. 11, the unevenarea of polishing that is seen in the vicinity of 50 mm from the centerof the wafer as observed in FIG. 7 is eliminated. The polishinguniformity (σ) was 6.3%. The reason for this is considered as follows:specifically, as a result of the central bored part being created as aregular hexagonal shape, the distance from the center of rotation to theboundary between the bored part and non-bored part changes along withthe rotation of the pad, so that the area at this boundary is smoothed.Accordingly, if the shape of this bored part is a shape other than acircle, the same effect is obtained. From a similar point of view, ifthe center of the bored part is shifted from the center of rotation ofthe pad, the same effect is also obtained.

[0094] (Embodiment 3)

[0095]FIG. 12 is a plan view of the polishing pad constituting the thirdembodiment of the present invention. This polishing pad has a similarconstruction to the pad shown in FIG. 5(a), in which a circular boredpart is provided in the central part of an equilateral triangle that hasrounded corners. When the radius of this circular bored part is r, thispolishing pad is designed so that the length of the portion that is r1away from the center O of this polishing pad (i.e., on the circumferencewith a radius of r1) and contributes to the polishing is within therange of 0.5 πr to 4 πr.

[0096] In the case of FIG. 12, when the circle with a radius of r1internally contacts the equilateral triangle, the length of the portionon this circumference that contributes to the polishing is maximum.Accordingly, the bored part may be designed so that the radius of theinternally contacted circle is twice or less of the radius of the boredpart.

[0097] In the portion where the radius is larger than the radius of theinternally contacted circle, the length of the portion that does nottouch the polishing pad is increased as the radius becomes larger, sothat the length of the portion that contributes to the polishing isreduced. Accordingly, in cases where the radius is increased up to theareas excluding the portions that are located within 5 mm of the endparts, i.e., of the vertices A, B and C of the equilateral trianglecreated by extending the lines forming the edge portions of thepolishing pad (sides of the triangle), the polishing pad may be designedso that the length of the portion that contributes to the polishing inthis range is 0.5 πr or more.

[0098] (Embodiment 4)

[0099]FIG. 13 is a flow chart which illustrates the semiconductor devicemanufacturing process. The semiconductor device manufacturing process isstarted, and in step S200, an appropriate processing step is firstselected from steps S201 through S204 described below. The processingthen proceeds to one of steps S201 through S204 in accordance with thisselection.

[0100] Step S201 is an oxidation process in which the surface of thesilicon wafer is oxidized. Step S202 is a CVD process in which aninsulating film is formed on the surface of the silicon wafer by CVD,etc. Step S203 is an electrode formation process in which electrodes areformed on the silicon wafer by a process such as vacuum evaporation.Step S204 is an ion injection process in which ions are injected intothe silicon wafer.

[0101] Following the CVD process or electrode formation process, theprocessing proceeds to step S205. Step S205 is a CMP process. In thisCMP process, planarization of the interlayer insulating film or theformation of a damascene, etc., by polishing of the metal film on thesurface of the semiconductor device is performed using the CMP apparatusof the present invention.

[0102] Following the CMP process or oxidation process, the processingproceeds to step S206. Step S206 is a photolithographic process. In thisphotolithographic process, coating of the silicon wafer with a resist,burning of a circuit pattern onto the silicon wafer by exposure using anexposure apparatus, and development of the exposed silicon wafer, areperformed. Furthermore, the next step S207 is an etching process inwhich portions other than the developed resist image are removed byetching, and the resist is then stripped so that the resist that hasbecome unnecessary following the completion of etching is removed.

[0103] Next, in step S208, a judgement is made as to whether or not allof the required processes have been completed. If the required processeshave not been completed, the processing returns to step S200, and theprevious steps are repeated, so that a circuit pattern is formed on thesilicon wafer. When it is judged in step S208 that all of the processeshave been completed, the working process is ended.

[0104] In the semiconductor device manufacturing method of the presentinvention, the CMP apparatus of the present invention is used in the CMPprocess; accordingly, the uniformity of polishing in the CMP process isincreased. As a result, the present invention has the following effect:namely semiconductor devices that have fine patterns can be manufacturedat a lower cost than is possible in conventional semiconductor devicemanufacturing methods.

[0105] Furthermore, the CMP apparatus of the present invention may alsobe used in the CMP process of semiconductor device manufacturingprocesses other than the semiconductor device manufacturing processdescribed above.

INDUSTRIAL APPLICABILITY

[0106] As was described above, the CMP apparatus of the presentinvention can be used for polishing the surface of a wafer, for example,in semiconductor device manufacturing processes. Furthermore, thesemiconductor device manufacturing method of the present invention canbe employed for manufacturing semiconductor devices that have highdegree of pattern density.

1. A CMP apparatus (chemical mechanical polishing apparatus) whichperforms polishing by pressing a polishing pad that is smaller than theobject of polishing against the object of polishing in relative termsand by swinging the polishing pad while rotating both the object ofpolishing and the polishing pad so that relative movement occurs betweenthese two parts, wherein this CMP apparatus comprises a polishing padwhose shape is such that in all points on the surface of the object ofpolishing, the product of three values—i.e., the integrated value of therelative linear velocity, the integrated value of the pressure, and theintegrated value of the contact time—of the polishing pad and object ofpolishing during the polishing time is within ±30% of the mean value ofthe product of these three integrated values at all points on thesurface of the object of polishing.
 2. The CMP apparatus described inclaim 1, wherein at least one bored part is provided in the polishingpad.
 3. The CMP apparatus described in claim 2, wherein the area of thebored part is 80% or less of the total area of the pad.
 4. The CMPapparatus described in claim 2, wherein a mechanism for supplying aslurry from the bored part is provided.
 5. The CMP apparatus describedin claim 2, wherein the shape of the above-mentioned bored part is ashape other than a circle.
 6. The CMP apparatus described in claim 1,wherein a circular bored part is provided in the center of the polishingpad, and when the radius of this bored part is r, the length of theeffective part of the polishing pad on the circumference in thespecified distance from the center of the above-mentioned polishing padis in the range of 0.5 πr to 4 πr, excluding the end parts of theabove-mentioned polishing pad.
 7. The CMP apparatus described in any oneof claims 1 though 6, wherein the center of the external shape of thepolishing pad and the center of rotation of the surface plate to whichthe polishing pad is pasted are shifted.
 8. A semiconductor devicemanufacturing method comprising a process in which a wafer is polishedusing the CMP apparatus described in any one of claims 1 though
 6. 9. Asemiconductor device manufacturing method comprising a process in whicha wafer is polished using the CMP apparatus described in claim 7.